Hot Topic November 2024: New Study Suggests Foods Rich in Live Microbes Benefit Mortality & Aging

A healthy and balanced intestinal microbiome is an important component of both overall health and optimal wellness during the aging process.^1,2 Supporting commensal and symbiotic microbes in the gut through diet and lifestyle helps to maintain intestinal, metabolic, and systemic immune homeostasis.^3-7 Nutritional and lifestyle interventions that enhance gut health have also been associated with reduced biological age.^8-10

Research studies have recently focused on how diets containing fermented foods that contain live microbes impact gut, immune, and metabolic health. A 2021 randomized clinical trial, for example, compared the effects of two microbiota-targeted diet interventions, one with plant-based fiber and the other with fermented foods, on the gut microbiome and the immune system in healthy adults.¹¹ After 10 weeks, in contrast to the high-fiber diet, the fermented food diet significantly decreased inflammatory markers and increased microbiota diversity from baseline levels.¹¹ Further, a 2023 observational study found that higher dietary consumption of live microbes in foods was associated with lower systolic blood pressure, C-reactive protein, plasma glucose, plasma insulin, plasma triglycerides, waist circumference, and BMI levels, as well as higher levels of high-density lipoprotein cholesterol among adults in the US.¹² Now, a new observational study has investigated the associations between mortality and biological aging and the consumption of foods with low, medium, or high live microbe content.¹³

Eating Live Microbes: Mortality & Aging Benefits

The 2024 Zhu et al observational study has established a correlation between dietary consumption of live microbes found in foods such as fermented dairy products, sauerkraut, miso, and some fresh fruits and vegetables eaten unpeeled and a reduced risk of all-cause and cardiovascular mortality as well as a decelerated progression of biological aging.¹³

This study used data from the cross-sectional 1999-2018 National Health and Nutrition Examination Survey (NHANES), which included 24-hour dietary recall questionnaires.¹³ The analysis included a total of 34,133 US adults from the NHANES data set that had an average follow-up period of 9.92 years. The adults were categorized into either low, medium, or high dietary live microbe groups based on the foods they reported in their dietary recalls. Researchers also combined the amounts of medium and high-level foods consumed per person and defined this as the medium-high consumption category. 

Investigators applied a previously used classification system¹⁴ to determine if foods contained low (<104 colony-forming units per gram [CFU/g]), medium (104-107 CFU/g), or high (>107 CFU/g) levels of live microbes. These levels reportedly reflect the approximate numbers of live microbes in different types of foods such as pasteurized foods (low level), unpeeled fresh fruits and vegetables (medium level), and unpasteurized fermented foods (high level). Of note, probiotic supplements were not included in the food analyses. 

Researchers from the study reported the following health, chronic disease, mortality, and biological aging results:¹³

• The male, overweight prevalence, and smoking groups were most often associated with the low microbe group.
• The highest education and income levels and highest levels of alcohol intake and physical activity were found in the high microbe group and gradually decreased in the medium and low microbe groups.
• Compared to the low microbe group, the medium and high microbe groups showed a lower prevalence of hypertension, cardiovascular disease, diabetes, and chronic kidney disease.
• Compared to the low microbe group, those US adults in the medium microbe group had a significantly lower risk of all-cause mortality (HR: 0.88) and cardiovascular mortality (HR: 0.86) during the follow-up period. 
• Compared to the low microbe group, those US adults in the high microbe group only showed a significant lower risk of all-cause mortality (HR: 0.69) and cardiovascular mortality (HR: 0.63) in the unadjusted models. Fully adjusted models (i.e., when variables such as gender, age, BMI, etc. were considered) reflected reduced but nonsignificant results for all-cause mortality risk (HR: 0.92; CI: 0.82-1.03) and cardiovascular mortality risk (HR: 0.83; CI: 0.68-1.00). 
• They found that every 100 g of medium-high group foods consumed was significantly associated with a 6% reduced all-cause mortality (HR: 0.94) and a 9% reduced cardiovascular mortality (HR: 0.91) but not with cancer mortality during the follow-up period.
• Compared to the low microbe group, the medium microbe group had a 0.22-year younger biological age using the Klemera–Doubal method (KDM) biological age algorithm and a 0.19-year younger PhenoAge.
• Compared to the low microbe group, the high microbe group had a 0.33-year younger KDM biological age and a 0.32-year younger PhenoAge.
• ln addition, each additional 100 g of medium-high group foods consumed was associated with decreased KDM biological aging acceleration and decreased PhenoAge acceleration.

The researchers reflected on the limitations of their study, which included residual or unknown confounding variables, response biases due to the use of questionnaires, and dietary recall limitations due to memory or recall issues. In addition, this study used cross-sectional data that only offers a snapshot of an individual’s dietary intake, and the use of 24-hour questionnaires may not accurately reflect consistent dietary habits. Even with these limitations, the investigators concluded that high dietary intake of live microbes was associated with a reduced risk of mortality and a deceleration of biological aging.¹³

Mortality risks and healthy aging are at the forefront of concerns for many patients, and modifiable lifestyle factors such as diet play a significant role in optimizing longevity and enhancing both gut and overall health. This study continues to emphasize the importance of a diverse diet of whole plant foods, fiber-rich sources, and those foods that contain beneficial microbes that support intestinal health and maximize the abundance of commensal gut microbiota and their health-promoting metabolites.